By Alonso Soto

BRASILIA (Reuters) - The founding members of Mercosur will give Venezuela until Dec. 1 to meet its membership requirements or be suspended from the trade bloc, Brazil said on Tuesday, in the latest twist in a row that has exposed ideological divisions.

The ultimatum will further isolate the socialist-led nation, which has been at the center of a fight over the rotating presidency of Mercosur, which has turned to the right after years dominated by leftist governments.

Brazil's Foreign Ministry said in a statement that decision was meant to "preserve and strengthen Mercosur."

Argentina, Brazil, Paraguay and Uruguay also decided in a deal first reported by Reuters to share the presidency of the group in a temporary solution to the group's currently being without a head.

Venezuela's information ministry did not immediately responded to requests for comments.

All Mercosur members but Uruguay blocked Venezuela from assuming the rotating presidency in June, accusing the OPEC nation of failing to incorporate a joint economic accord and a commitment to protect human rights.

The bickering over leadership has stalled Mercosur's everyday operations and trade negotiations with other countries, ultimately forcing Uruguay to accept a tougher stance against Venezuela, a Brazilian official familiar with the matter said.

Facing food shortages and political turmoil, Venezuelan leftist President Nicolas Maduro has come under greater international pressure to cede to opposition calls for a recall vote on his leadership this year.

"Having that Mercosur membership is seen as important by the Venezuelan regime to show its population that it is integrated in the region," said Oliver Stuenkel, professor of international relations at Sao Paulo-based think tank FGV. "This will certainly add pressure, but is unlikely change things in Venezuela."

Brazilian diplomats have said that until late August Venezuela had met about 30 percent of the membership requirements, which entails adopting a series of rules to facilitate trade inside the group. Venezuela was initially admitted in the bloc in 2012 and given four years to meet all the requirements.

Brazil's new President Michel Temer, a center-right politician who replaced leftist Dilma Rousseff after she was impeached in August for breaking fiscal rules, has led the charge to undermine Venezuela in the bloc.

After Temer, who was Rousseff's vice-president, permanently assumed the presidency until the end of the term in late 2018, Venezuela froze ties and recalled its ambassador in Brasilia. The leftist governments of Ecuador and Bolivia, once close allies to Brasilia, also recalled their ambassadors.

The widening political divisions in South America also reflect the changing luck of a region struggling with a drop in global commodity prices after a decade-long boom that helped leftist leaders raise spending on the poor.

(Additional reporting by Alexandra Ulmer; Writing by Alonso Soto; Editing by Leslie Adler and Nick Macfie)